1. Field of the Invention
The present invention relates generally to instrumentation for measuring the weight of an object, and more specifically to a pneumatic device for weighing a truck having a pneumatic suspension system. The device comprises a pneumatic pressure gauge calibrated to show the weight of the trailer, and connected to the pneumatic suspension system of the trailer and/or tractor.
2. Description of the Related Art
The trucking industry is a vital part of the U.S. economy, and as such, thousands of trucking companies, ranging from small, local single truck operators to larger interstate operations having hundreds of trucks, have been formed. Such trucking operations are heavily regulated, due to the size and weight of the vehicles used. Some of the most critical regulations in the trucking industry relate to the maximum allowable loaded weight of the truck. Most, if not all, states have developed regulations relating to the maximum allowable weight of trucks and other vehicles used in commercial operations within each state. These regulations are of sufficient importance, that it is difficult to find a major stretch of U.S. highway more than two hundred miles or so in length, without truck weight scales.
Truck weight is of importance for several reasons, such as licensing revenue, etc. However, safety is a much more important concern. Limits are placed upon truck weight due to highway and bridge weight bearing capacities, and also for the well known reason that the heavier a vehicle is, the more difficult it is to maneuver and stop that vehicle. Generally, most states place a maximum limit of about 72,000 pounds total weight for a fully loaded "eighteen wheeler" semi-truck tractor and trailer, but this may vary from state to state, and may even vary within a state depending upon the type of truck and/or cargo being carried.
To this point, the only means truckers have of determining the fully loaded weight of their trucks, is by driving the truck onto a truck scale. Practically all trucking companies have such scales, but they are of no use when a truck is sent out empty to pick up a load at another location. At that point, the only recourse a trucker has is to know the empty weight of his truck and trailer, and trust that the cargo manifest is correct.
What is needed is a simple and inexpensive means for a truck driver to determine the weight of the loaded truck and trailer combination, easily and quickly. While at least one other device has been developed for installing within a vehicle for determining the weight of the vehicle (as discussed further below in the discussion of the related art), that device is exceedingly complex and costly. A discussion of the related art of which the present inventor is aware, and its differences and distinctions from the present invention, is provided below.
U.S. Pat. No. 3,910,365, issued on Oct. 7, 1975 to Buchele, describes a device having an upper liquid chamber and a lower air chamber, with means provided for adjusting the air pressure in the lower chamber to compensate for tare weight. The Buchele device is not adaptable for use in motor vehicles, as such vehicles universally use multiple point suspension systems and a plurality of axles, rather than the single point attachments of the Buchele device. The present invention is adapted for use with motor vehicles, particularly trucks, having pneumatic or air suspension systems, and having a plurality of suspension points and axles in the suspension system.
U.S. Pat. No. 4,733,564, issued on Mar. 29, 1988 to Gorge, describes a device comprising an aneroid chamber and spring loaded gear train to reduce or eliminate play and hysteresis in the mechanical movement. No suggestion is made of any means of calibrating the gauge to measure the weight supported by a pneumatic suspension system, as in the present invention.
U.S. Pat. No. 5,170,856, issued on Dec. 15, 1992 to Yang, describes a pair of hydraulic cylinders used to measure the force required to displace the hydraulic fluid therein, with some mechanical resistance being provided by a series of peripheral supports to the scale platform. The second cylinder bears against an electronic load cell or the like. No connection to a pneumatic suspension system is disclosed by Yang.
U.S. Pat. No. 5,179,856, issued on Jan. 19, 1993 to Huang, describes an electronic device to measure and display pressure sensed by a sensing element. While Huang states that the readout may provide an indication of pressure in different units, the exemplary units disclosed are pounds per square inch (PSI), kilograms per square centimeter, and bars (100 kN per square meter). Huang makes no suggestion of calibrating his gauge to measure the weight in pounds of an object supported by a pneumatic system, as provided by the present invention.
U.S. Pat. No. 5,349,866, issued on Sept. 27, 1994 to Huang, has a Bourdon tube or aneroid chamber used to move a lever against a piezoelectric resistor element. The variable electrical current is used to provide a digital display of the pressure. The particular structure of this gauge is irrelevant to the concept of the present invention, in which a gauge of any suitable type is used to display the pressure readout in weight from the pneumatic suspension of a truck or other motor vehicle. Huang makes no suggestion of calibrating his gauge to provide an indication of weight.
U.S. Pat. No. 5,391,843, issued on Feb. 21, 1995 to Sato et al., describes a complex electronic pressure and inclination sensing system. The pressure sensors are for use in pneumatic-hydraulic suspension cylinders, rather than in a strictly pneumatic suspension. Such pneumatic/hydraulic suspension devices also act as shock absorbers and include a pressurized gas, e. g. nitrogen, at the time of manufacture, with no significant weight being supported by the device, in order to provide some resilience for the device due to the otherwise incompressible hydraulic fluid. This preloading of the device makes any pressure measurement of a load supported thereby, inaccurate unless the preload is compensated for. The present load measuring system is adapted for use with purely pneumatic suspensions, and no such pressurized preload need be compensated for. Also, the present load measuring system is a strictly pneumatic and mechanical system, devoid of electronics. Thus, the present device and system is considerably more economical and easier to maintain than the electronic system of Sato et al.
U.S. Pat. No. 5,555,764, issued on Sept. 17, 1996 to Dybas, discloses a specially constructed base for a propane cylinder, with the base including a pressure gauge installed integrally therewith and communicating with a central chamber in which the pressure varies depending upon the weight of the overlying propane tank or cylinder. Dybas describes the gauge as being calibrated to indicate the weight of the cylinder, but the Dybas device cannot be used to measure the weight of a motor vehicle with its numerous pneumatic suspension springs, due to its integration into a single pneumatic component. Also, Dybas does not disclose marking his gauge with any limits, nor any visible or audible annunciator for a predetermined limit.
U.S. Pat. No. 4,854,407, issued Aug. 8, 1989 to Wagner, discloses a system for registering the load distribution of a trailer over the front, drive and trailer axles with respect to the fifth wheel disposition and an established total air pressure in the system. Supplemental dials are adjusted to align an estimated weight with the total air pressure reading thereby giving the operator a pressure related estimate of the loads carried on each axle. Wagner does not discloses a pointer adjustment in order to accurately calibrate the gauge to a known weight quantity.
U.S. Pat. No. 4,832,141, issued May 23, 1989 to Perini et al., discloses a vehicle mounted load indicator having a displacement detecting unit for monitoring the change in distance between a vehicle axle and the load platform. Upon sensing a change in displacement, the air pressure is adjusted so as to return to the original distance. Perini et al. does not discloses a method to adjust a gauge pointer in order to accurately calibrate the gauge to a known weight quantity.
U.S. Pat. No. 4,792,004, issued Dec. 20, 1988 to Sheffield, discloses a pressure gauge for use on farm equipment to measure the pressure in the hydraulic system of the equipment. The operator must perform a mathematical algorithm in order to determine the weight of a payload. Sheffield does not disclose a method to adjust a gauge pointer in order to accurately calibrate the gauge to a known weight quantity.
U.S. Pat. No. 5,844,474, issued Dec. 1, 1998 to Saling et al., discloses an overload alarm attached to a vehicle suspension unit. The overload alarm includes a limit switch which actuates a visual and audible indication upon the detection of an excessive weight on the vehicle. Saling et al. does not discloses a pointer adjustment in order to accurately calibrate the gauge to a known weight quantity, nor does Saling et al. disclose a method to adjust a gauge pointer in order to accurately calibrate the gauge to a known weight quantity.
None of the above inventions and patents, either singly or in combination, is seen to describe the instant invention as claimed.